Removal of suspended solids from oil



July 19, 1938. v 3 5, -r 2,124,148

REMOVAL or SUSPENDED SOLIDS FROM OIL Filed Nov. 18, 1955 JnVenior 00mm5. NUTT Patented July 19, 1938 UNITED STATES 2,124,148 I L REMOVAL OFsusrgi nnn sou s mom Donald B. Nutt, El Segundo, Calit, assignor toStandard Oil Company. of California, San Francisco, Calif., acorporation of Delaware Application November 18, 1935, Serial No. 50,415

6 Claims. (01. 196-147) This invention relates to a method of treatingoil to remove particles of solid matter carried in suspension therein.

It is well known that petroleum oils, particularly light distillates,both straight run and those derivedfrom thermal cracking operations, areoften subjected to treatment with reagents which introduce finelydivided solids into the treated oil. For example, such oils maybetreated with sodium plumbite solution and sulfur, or directly with asuspension of lead sulfide in caustic soda solution. Such treatmentimproves the odor of the oil by converting mercaptans to oil-solubledisulfides which have an unobjectlonable odor. It is customary, intreating oils with suchreagents, to follow the contacting step'with asettling step (for example, the oil containing suspended matter may bepassed through a zone of low velocity wherein the major portion of the20 suspended matter settles out by gravity);

The supernatant oil, even in plants provided with a relatively verylarge settling capacity, is found to contain a material quantity ofextremely -fine1y divided reagent and sulfide particles in suspension.This suspended matter may be removed by water washing, but such methodentails serious practical disadvantages. Among those disadvantages maybe mentioned the tendeney to wash out the reagent liquid only, withouteffecting complete removal of the very minute, even colloidal, solidparticles, allowing such particles to remain suspended in the oil. Otherdisadvantages of the washing method are theinccreased cost due to waterpumping and equipment, the tendency to emulsion formation-(resulting inoil loss), and the necessity for drying the water washed oil. I i I a iAnalternative method of removing these suspended materials is to passthe oil containing such suspension through a filter. The disadvantagesof this'procedure are'obvious.

Various well known treating methods, other than those mentioned above,introduce finely divided solids into the treated oil, and present thesame problem of clean separation. Among these may be mentioned treatmentof light oils with aqueous caustic solution containing powdered charcoalor metallic (lead, cobalt or nickel) sulfide and nickel sulfide inammonia.

ficultly removable suspended solids may be separated from oils in acontinuous mannerwithout suffering any of the disadvantages attendantupon the known methods of removal. This I accomplish by passing the oilcontaining finely I have discovered a method whereby such difdividedmaterial in suspension through a bed of solid insoluble coarse materialsuch as crushed rock, loosely packed and coated with an aqueous film. Ifthe bed is of sufilcient size as compared with the volume of oil to bepassed over it, the oil delivered from. such bed will be entirely dryand free from foreign matter. No water washing or filtration or otherprocedure is then necessary. Moreover, the reagent removed by'this bedis in such condition that it'may be, if desired, restored directly to anemcient treating agent ,by any of the well known reclaiming processes.The bed is so constructed as to remove all of the suspended matter. Inaccordance with my invention the bed is so constructed as to affordrelatively large voids or passageways for the oil, such that longcontinued operation will not resultin the cloggingof the bed witharrested solids. Furthermore, the aqueous film or coating material onthe surfaces of the packing of the bed, in addition to its function ofentrapping solid particles from the oil stream, acts to maintain thecontinued free flow of oil by its tendency to drain outslowly bygravity, carrying with it accumulated solids. It is evident, therefore,that my invention is not to be confused with filtration, wherein thesolids are removed by straining through a mesh, the passages or voidsofwhich are in effect smaller than the solid particles.

As previously stated, it is necessary, according to my invention, thatthe bed be coated with an aqueous liquid. Preferably-fuse a solution ofcaustic alkali. An aqueous solution of sodium or potassium hydroxideorsodium plumbite is particularly desirable. The coating may be formedby introducing the coating liquid in admixture with the incoming oil, orseparately into the top .of the bed, whereby it will run slowly downthrough the packing countercurrent to the oil. In practice, however,many of the treated oils which contain solids in suspension also containfinely divided droplets of caustic solution, e. g. in a the case ofdoctor" (sodiumplumbite) treated oils. In such cases the caustic reagentsupplies the necessary coating for the bed.

The action of the bed is, as I believe, as follows: The aqueous'coatingmaterial (or the suspended reagent carried by the oil which flowsthrough the bed) is retained preferentially by the solid surfaces of thebed, thus coating these surfaces with thedesired liquid film. Thesuspended solidparticles and additional droplets of added coating liquidor, suspended reagent adhere to and are retained by this film. As thefilm increases in thickness, it tends to run oflf, carrying orreclaimed, -as desired.

with it all of the particles which it contains. Thus the coatingmaterial continually drains toward the bottom of the bed, where areservoir is provided, from which reservoir 8. draw-off line, controlledby a valve, permits the operator to remove it. Particles-of sulfide orother solid, or droplets of sulfide-plumbite (or sulfide-caustic)suspended in oil, are not removable by a bed such as has been describedabove unless and until the surfaces of the bed have been coated with afilm as described. Once this has been done, such a film will retainpreferentially all particles and droplets which come in contacttherewith. It is necessary, in order that all suspended matter may beremoved, that the bed shall contain sufficient surface to insure contactwith all of the suspended matter carried by the oil which passes throughthe bed. It is also necessary that the voids of the bed be of sufilcientsize as to preclude the eventual clogging of the bed by accumulatedreagent, and also so as to preclude such a high oil velocitytherethrough that portions of the reagent adhering to the surfaceswithin the bed will be swept oh and carried along with the oil.

In order that the. operation of my invention may be more clearlyunderstood, reference may be had to the attached drawing, whichrepresents diagrammatically one form of apparatus in which theinventionmay be carried out.

In the drawing, l represents a pipe line leading from a treating plant,not shown. The line I is connected as shown with one end of a settlingvessel 2, the interior of which is free from packing or otherobstruction. A pipe line 3 leads from the lowest point of the settler 2.The pipe line I is equipped with a valve 4. A pipe line 5 is connectedwith the upper portion of the settler 2 and leads into the lower portionof a vertical vessel 6. The pipe line 5 ends, within the vessel 6, in asuitable distributing head H. The vessel 6 is equipped with a transverseforaminous grid or screen support 8, this grid being positioned at apoint below the distributor head H.- Resting on the grid. 8 is aloosely; packed bed of crushed rock of sufiicient depth to submerge andto extend a considerable distance above the distributor II. This bed isindicated in the drawing by the shaded area 1. The lowermost portion ofthe vessel 8 is equipped with a draw-oil. line 9 containing a valve III.A clean oil exit line [2 leads from the upper portion of the vessel 6 toa storage tank I3. Line ll equipped with a valve l5, and line l6equipped with a valve l1, lead from a supply .of caustic solution, notshown.

An example of operation 'of the equipment shown diagrammatically in thedrawing is as follows: A mixture of oil containing in suspension sodiumplumbite and lead sulfide flows through line I into the open settler 2.'Within the settler 2 the velocity of the liquid is greatly decreased,permitting the major portion of the suspended matter to settle out bygravity. The material which settles out collects in the lower portion ofthe vessel '2 and is drawn ofi continuously or intermittently throughline. 3 by manipulation of valve 4. The material thus drawn ofl may berecycled for further use in contacting additional oil, or it may be.stored The liquid flowing from the vessel Zthrough line 5 is oilcontaining finely dispersed droplets of plumbite and particles of leadsulfide. This contaminated oil enters the vessel 6 through thedistributor head 'the "oil flowing across such surface.

I have discovered, the minute droplets of plumbite solution will adhere.Thus in a short time the rock becomes coated with solution, whichcoating thenceforth collects and retains any particles of lead sulfidewhich may be carried by The bed is of suificient depth to insure thethorough contacting of all portions of the oil with the solid surfacesof the bed. The oil which leaves the vessel 6 through line I! is foundto be perfectly bright and free from suspended foreign matter. As theoperation continues the bed becomes coated with more and more of theplumbite and a downward drainage of lead sulfide and plumbite takesplace. The material thus draining downwardly collects in the lowerportion of the vessel 6 and is drawn oil continuously or intermittentlythrough line 9 by manipulation of valve ID. The material flowing throughline 9 may be combined with that flowing through line 3 previouslydescribed.

Although the above-described example of the operation of my inventionrelated to the cleaning of an oil which. had been "doctor treated, itwould also apply to an oil containing suspended water, liquid causticmaterial and solid particles.

In the event the oil contains solids only, or in starting operation,.thenecessary bed coating is preferably established and maintained byadmitting water or, preferably, caustic solution through line l8,valvel1, into the upper portion of the bed. Alternatively, this causticmay be introduced through line I4, valve IE, to the stream of oil on itsway to the packed vessel 6. In the latter event, unless the turbulancein line 5 is unusually great, it is desirable to inject the materialfrom line H into line 5 through an atomizing device in order to disperseit thoroughly in the oil.

Although the size and other details of construction of the apparatus,particularly the purifier i, may be varied to suit the needs ofindividual cases, I have found that a satisfactory apparatus for thetreatment of 45,000 gallons of cracked naphtha per hour is a 10 foot by30' foot vertical drum packed with No. 4 rock to a depth, above the oilinlet ll, of about 18 feet.

Rock conventionally termed No. 3 rock, ranging from about to inch indiameter, may be used satisfactorily. The bed should not be formed ofmaterial finer than No. 4 rock, however. No. 4 rock will pass a inchmesh sieve, 45% to 50% will pass inch mesh, not more than 2% to 3% willpass inch mesh. If material finer than No. 4 is used (blast sand, forexample), the voids are sosmall that considerable pressure is requiredto force the oil through the bed, and there is a tendency for theaqueous liquid and the solid particles to clog a large number of thevoids, resulting in channelling and destroying, or greatly reducing, thedesired drainage of caustic. fromthe bed. A proper bed for my purpose isone containing 40%.to 65% voids averaging from 0.003 to 0.06 square inchin cross-section.

It is not necessary that rock be used as packing for the vessel 6. Otherinsolubleand nonreactive solids preferentially wetted by water orcaustic may be used, e. broken glass, brick or pottery.

The settler 2, shown in the drawing as inclined at about 30, may, ofcourse, be placed in a vertical or horizontal position. Likewise, thevessel 6 may be in a position other than vertical, although the verticalposition is preferred as it is convenient and has a large throughputcapacity for a given quantity of rock.

Having thus described my invention, I claim:

1. A method of removing finely divided solid particles from oilcomprising passing the oil containing solids in suspension through thevoids in a nod of solid issoluble material, such voids being very largerelative to the size of the solid particles, and maintaining thesurfaces of the said solid material coated with aqueous alkalinesolution.

2. A method of removing finely divided solid particles from oilcomprising passing the oil containing such particles in suspensionthrough the voids of a bed of solid material insoluble in oil and water,said voids being sufiiciently larger than the suspended particles as toproelude clogging thereof by accumulations of solid particles,maintaining the surfaces of said solid material coated with an aqueousalkaline solution.

A method of treating oil containing in suspension aqueous alkalinesolution and finely divided solid particles, comprising passing such oilin contact with extended surfaces of solid insoluble material to coatsaid surfaces with a film of aqueous alkaline solution and retain saidsolid particles in said film.

4. A method of removing finely divided solid particles from oilcomprising passing the oil through the voids of a bed of solid materialinsoluble in oil or caustic, said voids having an averagecross-sectional area of from 0.003 to 0.06 square inch, maintaining thesurfaces of the solids of said bed coated with aqueous alkalinesolution.

5. Arnethod of treating oil containing suspended solids comprisingpassing such oil in contact with extended surfaces of solid insolublematerial coated with a. film of aqueous alkaline solution, whereby thesuspended solids are retained in said film.

6. A method of removing finely divided solid particles from oilcomprising passing the oil con taining solids in suspension through thevoids in a bed of solid insoluble material, such voids being very largerelative to the size of the solid particles, and maintaining thesurfaces of the said solid material coated with sodium plumbitesolution.

DONALD B. NUTT.

